1. Field of the Invention
This invention relates to a priming system for propellants having a thermal decomposition point above 180.degree. C. More particularly this invention relates to a priming system for such propellants characterized in that the priming system contains a known ignition charge, together with a booster charge, the booster charge being of a solid explosive compound containing one or more --NO.sub.2 and/or --N.dbd.N end groups and 10 to 60 weight % of an initiating explosive.
2. Discussion of the Prior Art
The priming systems known hitherto for case-less ammunition are based on nitrocellulose, sometimes mixed with other gas-yielding substances, such as glycerin trinitrate. These propellants have thermal decomposition points up to a maximum of 180.degree. C.; they can be ignited perfectly well by the known priming mixtures based on initiating explosives or pyrotechnical mixtures.
The above-mentioned known propellants, however, have been improved so as to have greater animal stability. These more stable propellants contain organic compounds having terminal &gt;N--NO.sub.2 groups or heterocyclic aliphatic and aromatic compounds whose thermal decomposition points are in some cases appreciably higher than the decomposition point of nitrocellulose, which is 170.degree. to 180.degree. C.
The ignition of these high temperature-resistant propellants which the known priming mixtures based on initiating explosives involves considerable difficulty. The ignition must be accomplished such that the propellant will be completely burned up by the initiated chemical reaction, leaving no solid residues; on the other hand the priming mixture must not be so powerful as to transform the desired burning action to a detonation.
Attempts have been made to ignite such propellant charges with the known priming charges. To obtain a continuous ignition, however, it was found necessary to increase the power of the priming charge in relation to the normal, nitrocellulose-based propellant. This increase of power alone, however, did not result in a uniform and complete reaction of the propellant. Additionally therefore, the geometrical shape of the propellant charge had to be modified such that the ignition spurt of the primer would contact the maximum surface area of the propellant. This was achieved, for example, by shaping the propellant charge into an elongated hollow cylinder or hollow block, so that the ignition spurt contacted nearly the entire inside surface of the hollow body. The wall thickness of the hollow body must be slight, so that the heat produced by the ignition will be transferred over as large an area as possible and the reaction will progress uniformly even within this thin layer and not stop half-way through it.
This type of construction involves disadvantages in the manufacturing process. Also, it has its limitations with regard to the geometry which make it impossible to take advantage of the other benefits which are offered by the use of case-less ammunition.